Specifications for word clock?

[irrigating]

I need to know the specifications for word clock, and how it relates to AES/EBU S/PDIF and S/PDIF-2. I'd like to sync my ADC/DAC convertors to an external sync box that outputs word clock. Is it the master clock signal already present at my convertors, or is it something entirely different?

Any help would be appreciated.

Tom P.